1
SYLLABUS
SENSORIAL DISORDERS
COURSE NO. 13
D. BARÁKOVÁ, P. KUCHYNKA, I.KOCUR
2
INTRODUCTION
In the last ten years, the field of ophthalmology has remarkably changed. New
information about eye morphology and neural pathways, as well as a better
understanding of the functions of the eye and the pathophysiology of visual
functions, have facilitated the introduction of new methods and examination
techniques. The fast development of techniques has helped in improving and
accelerating the differential diagnosis and treatment of eye diseases. The
introduction of lasers in ophthalmology has created new ways of treating eye
disorders (e.g. glaucoma, diabetic retinopathy, intraocular tumors, secondary
cataract, etc.). The use of lasers in removing corneal tissue represents a
breakthrough in the field of refractive disorders. This has resulted in an increase
in the interest of ophthalmologists, as well as patients, in the field of refractive
surgery. The use of ultrasound in the treatment of cataracts was a remarkable
contribution, too. Phacoemulsification is routinely performed in the majority of eye
departments. In addition, lasers are gradually used in the treatment of cataracts
as well. This technique will be more popular in the near future. Ophthalmology is
a branch of medicine which requires full dedication, and knowledge is gained by
continuing the educational process.
What are the expectations of a student of medicine? The words of Professor
J. Kurz, who is the author of “Fundaments of eye medicine” published in 1949,
may suggest the answer: “Each medical student is supposed to gain knowledge
covering the whole of ophthalmology, and to learn the diagnosis and treatment of
fundamental diseases, since this task is highly relevant to his/her further career.
They must also know how to distinguish benign causes from those which are
dangerous for the patient and realize when their role is terminated.”
This is a syllabus, which represents an introduction to the field of ophthalmology
and is a brief guideline to help in the orientation and understanding of the main
issues.
3
Why does the patient usually come to see an ophthalmologist? It is mostly
because of
1. Uncommon appearance of the eye
2. Pain
3. Deterioration of vision
4. Trauma
5. Referred by other specialist
Uncommon eye appearance
Red eye - subconjunctival hemorrhage, inflammation of conjunctiva,
inflammation of cornea, anterior chamber hemorrhage, rubeosis iridis,
inflammation of sclera and episclera
Corneal opacities - corneal inflammation, scar, edema in acute glaucoma,
trauma, degenerative disease
Gray appearance of pupil - cataract, inflammatory exudate, occlusion of a pupil,
Irregular pupil - anterior synechias, posterior synechias, acute glaucoma
Iris irregularities - cyst, melanoma of iris
Different location of bulbus - exophthalmos,(endocrine orbitopathy, retrobulabar
tumour) enophthalmos (after trauma)
Different position of bulbus - squint
Reddish eye - blepharitis, hordeolum, chalazion, veruca, basalioma
Pain
Sharp, cutting - conjunctinal disorders
Foreign body - corneal surface trauma, edema, foreign body in conjunctiva or
cornea
Pain in a bulbus - iris inflammation, ciliary body (associated with acommodation
disturbance), acute glaucoma, (pain is progressing to adjacent areas, nausea)
Pain behind a bulbus upon movement - retrobulbar neuritis
Cephalea and astenophia - inappropriate refraction
Visual acuity disturbances’
Sudden loss of vision - total occlusion of central retinal artery
Sudden decreased vision - (falling black spots) hemorrhage in vitreous
4
Sudden decreased vision (affecting a visual field) - retinal detachment
Central scotoma - retrobulbar neuritis
Blurred vision - acute glaucoma, iritis, keratitis
Gradually decreased vision without pain - cataract, glaucoma
Sudden double vision - disorders of a muscle
Trauma
Trauma history is essential. Perforation of the bulbus containing an intraocular
foreign body may not be painful and therefore it may not be diagnosed properly.
Patient was referred by other specialists
They most frequently require an evaluation of sclerotic retinopathy, retinopathy
in hypertension, diabetic retinopathy. Gynecologists are interested in the potential
presence of retinopathy in pregnancy, neurologists require evaluation of the optic
disc regarding atrophy or edema.
Main fields of eye disorders:
Red eye
Cataract
Glaucoma
Diabetes mellitus
Intraocular inflammation
Intraocular tumors
Trauma
Squint
Refraction
Visually handicapped
5
RED EYE
Red eye can be found in external eye inflammation (inflammation of eyelids,
conjunctiva, cornea, episclera and sclera). It may be associated with disorders of
conjuctiva (iritis and cyclitis). Red eye is typically associated in disorders of
conjunctiva and means hyperemic conjunctival blood vessels. It is called
“injection” of conjunctiva.
The main causes are:
Mechanical irritation of conjunctiva –smoke, foreign body, dusty environment, etc
Inflammation of eye lids
hordeolum
chalazion
blepharitis (squamosa, ulcerosa)
abscess and flegmona
Viral inflammation of eye lids (herpes simplex, herpes zoster ophthalmicus)
Allergic inflammation of eye lids (drug allergy, pollen allergy )
Conjunctival inflammation
The clinical picture shows a red eye (hyperemic conjunctival blood vessels,
cutting, itching, feeling of a foreign body, lacrymation and secretion (serous,
mucous, purulent and mucopurulent). Injection (hyperemia) of conjunctiva can be
superficial, deep, mixed, pericorneal, local or diffuse. On the tarsal conjuctiva
there are follicles, papillae and occasionally membranes or pseudomembranes or
subconjunctival hemorrhages. In addition , the cornea, eyelids, episclera and
sclera can be affected. Treatment differs according to the type. Usually local
(antiseptic drops, adstringent drops, antibiotics in drops and oitments, corticoids
in drops and ointments), less often systemic treatment is required. The eye is not
patched.
6
Infectious conjunctivitis
Bacterial
Streptococcus pneumoniae, Haemophillus influenzae, Staphylococcus aureus
Viral
adenoviral keratoconjunctivitis, herpes simples virus
Chlamydial
Ch. trachomatis
Conjunctivitis in neonates
Neisseria gonorrhoeae, Herpes simplex virus
Immunology-related conjunctivitis
Allergic
Drug allergies, vernal keratoconjunctivitis, atopic and giant papillary conjunctivitis,
keratoconjunctivitis rosacea
Corneal inflammation
Infectious keratitis
Bacteria (Streptococcus pneumoniae, Staphylococcus aureus and epidermidis)
The clinical picture comprises red eye, pain, blurred vision, mixed injection,
cornea infiltration. There is a danger of corneal perforation if a corneal ulcer
develops and progresses.
Treatment: antibiotics, locally or systemically, depending on the grade of
inflammation. Locally in drops, ointments or subconjuctival injection. Mydriatics
prevent posterior synechiae and decrease pain. The eye is patched. Keratoplasty
is performed if the cornea is threatened by perforation.
Viral keratitis (Herpes simples virus, herpes Zoster virus)
Treatment :virostatics, corticosteroids, mydriatics
Mycotic keratitis (Candida albicans, Aspergillus, Fussarium)
Treatment: natamycin 5% drops, amphotericin B 0,2% drops, mydriatics
7
Non-infectious keratitis
Non-infectious conjunctivitis and corneal defects appear as a consequence of
immunological disorders or a systemic disease.( Mooren’s ulcer, interticial
keratitis, tuberculosis, mononucleosis, herpes zoster, herpes simplex, rubella)
Neurological disorders (neurothrophic keratitis, keratitis following lagophthalmos)
Inflammatody diseases of episclera and sclera
Episcleritis
Episcleritis is a benign disease, often recurrent. Clinically there is a red eye,
superficial local or diffuse congestion of blood vessels, or local surrounding
swelling is present. The eye is sensitive when touched. Antiflogistics are the first
choice.
Scleritis
Scleritis is a serious disorder, often associated with a systemic disease.
Congestion of blood vessels is deep. The eye is painful, protrusion of the bulbus
may be present, and movements are restricted. The disease is prolonged.
There are nodular, diffuse and necrotizing types. In necrotizing there can be
perforation and loss of the eye. In diffuse and nodular ones, NSAID is used, or
corticosteroids. In recurrences, immunosupresive drugs are involved. Necroizing
forms of scleritis are treated by immunosupresive drugs or in combination with
corticosteroids.
CATARACT
It is a leading cause of blindness worldwide. According to the WHO, 38 million
people went blind worldwide in 1990, 41.8% because of cataract . Cataract
surgery is the most frequent surgery performed on individuals aged 65 and over
in industrialized countries.
8
Cataracts can be acquired or inborn. The causes of cataracts are senility, trauma,
radiation, systemic diseases (diabetes, galactosemia, myotonic dystrophy), skin
disorders (atopic dermatitis, ichtiosis), central neural systemic disorders
(neurofibromatosis) and other diseases (glaucoma, uveitis, retinitis pigmentosa,
degenerative myopia, retinal detachment, tumors of ciliary body). Cataracts can
develop following the toxic influence of various drugs (corticosteroids,
antimalarics, amiodaron).
Hereditary cataracts can be found in childhood or later in life as a symptom of a
systemic disorder (myotonic dystrophy, Down’s syndrome, Edwards’ syndrome).
Infantile cataracts are always inherited , and the incidence is about 0.4% in
newborn children,. The most frequent causes are viral diseases in the mother
(rubella, toxoplasmosis), or the toxic influence of drugs used by a mother in early
pregnancy (corticosteroids). In more than a third of cases an etiology is not
detected.
Senile cataract is a multifactorial disorder. Risk factors are biochemical , genetic
and socioeconomic . Age is a main risk factor. Cataracts are rare in individuals
under fifty years of age, however, after eighty, it is found in 50% of people.
Regarding gender, cataracts are more often in women, mainly a cortical form. It
is also more frequent in blacks. An inherited predisposition and the influence of
malnutrition and being overweight have been proved. The satisfactory intake of
proteins, vitamins and other substances with an antioxidant effect is beneficial.
Cataracts are more frequent in patients with diabetes, hypertension, and in
people who smoke and abuse alcohol, etc. Corticosteroids, cholinergic drugs,
diuretics and chemotherapeutics induce cataracts. Radiation of a wavelength
higher than 295 nm can cause a cataract.
Lens opacities are associated with blurred vision and the projection of light.
Patients are disturbed by decreased vision in bright light and while driving at
night. Often there are defects in color vision and visual fields.
Cataracts strongly disturbing a patient in his/her everyday life should be operated
on. Indications for surgery are, therefore, different in each patient.
9
Phacoemulsification is the most frequently used method in cataract surgery.
Phacoemulsification is based on the utilization of ultrasound wave frequencies
higher than 30 kHz. The lens nucleus is destroyed mechanically by ultrasound
vibration, by cavitation effect and acoustic wave spread. An ultrasound probe
enters the eye via corneal or scleral incision. An intraocular lens is implanted
when the lens nucleus and residual lens tissue have been removed. Recent types
of intraocular lenses are made with soft materials, they are flexible allowing
implantation via an incision of 2.8-4.0 mm.
Currently cataract surgery is performed as an out-patient procedure under local
anesthesia. Both the minimal incision and soft intraocular lens implantation
facilitate early visual rehabilitation. People with cataracts are vastly improved
following surgery, thanks to the fast development of the technology employed and
new surgical appliances. In the near future, new minimized probes and the use of
“injectable” intraocular lenses are anticipated.
GLAUCOMA
Glaucoma comprises a range of disorders where the elevation of intraocular
pressure plays a crucial role in damaging nerve fibers and the papilla of the optic
nerve. It is a serious disease potentially leading to blindness.
Intraocular pressure induced by the production and outflow of aqueous fluid,
together with blood supply from the anterior part of optic nerve, are the major
components in the pathogenesis of glaucoma. Age, diabetes, history of
glaucoma in the family, hypotension, and other factors also play an important
role.
The current classifications of glaucoma are as follows:
Open angle glaucoma – intraocular pressure is elevated by an obstacle in the
trabecullar meshwork
Primary open angle glaucoma – elevation of intraocular pressure is not
associated with any other eye disease
10
Secondary open angle glaucoma – elevation of intraocular pressure follows
decreased aqueous fluid outflow (pigmentary glaucoma, pseudoexfoliative
syndrome, steroids induced glaucoma, inflammatory glaucoma, post-traumatic
glaucoma, etc).
Angle closure glaucoma – elevation of intraocular pressure follows narrowing of
the corneoscleral angle and the obstructing of the trabecular meshwork
Primary angle closure glaucoma- narrowing of the corneoscleral angle in
predisposed eyes
Secondary angle closure glaucoma - lens dislocation, intraocular tumors,
neovascular glaucoma, inflammatory glaucoma, post-traumatic glaucoma, etc.
Glaucoma in childhood represents a special group. It can be primary hereditary
glaucoma (buphthalmos, hydrophthalmos) when the elevation of the intraocular
pressure is caused by a decreased outflow in anomalies in the anterior segment
and secondary glaucoma (in metabolic disorders, tumors, following intrauterine
eye inflammation).
The medical history in patients with primary open angle glaucoma is mostly
uneventful. The majority of cases are found when screening patients for other
eye disorders. Patients usually complain only in later stages of the disease. At
that point there are already irreversible disorders of the optic nerve causing
scotomas, blurred vision and eventually the perception of colors when looking at
light and headache.
In patients with angle closure glaucoma there is more profound medical history.
Acute glaucoma means a sudden increase in intraocular pressure above
40mgHg, followed by headache, nausea, vomiting, and photophobia. Hyperemic
conjunctiva, opaque cornea, shallow anterior chamber and a dilated pupil that is
vertically oval, are frequently found symptoms.
An eye examination consists of : slit lamp examination (evaluation of anterior
chamber depth, pupil and iris), gonioscopy (grading of open angle, pathology
signs), ophhalmoscopy (changes of the optic nerve head – excavation, atrophy,
11
haemorrhage), tonometry (intraocular preassure measurement), perimetry
(scotomas), pathophysiological tests (VEP, ERG, contrast tests, color perception
of blue-yellow).
Treatment
Treatment of open angle glaucoma
To decrease amount of aqueous liquid produced.
1. Beta- blockers: (Timoptol, Vistagan, Betoptic) reduce the production
2. Adrenergic agonists: (Glaucon, D-Epiphrine) facilitate the outflow
3.Parasympatomimetics: (Pilocarpine, Isopto-Carbachol, Miostat) miotics,
facilitate the outflow
4. Inhibitors of carboanhydrasis (Trusopt) reduce the production
Treatment of secondary open angle glaucoma is similar to that stated above.
Treatment of angle closure glaucoma
1. Miotics
2. Osmosis active liquids (glycerine)
3. Laser treatment (laser trabeculoplasty, Nd:YAG-laser iridotomy, and
cyclophotocoagulation, Holmium laser or excimer laser sclerotomy)
4. Surgery (this allows an increase in the outflow intraocular liquid, by connecting
the posterior and anterior chambers, or a decrease in aqueous production).
Surgical procedures used are trabeculectomy, trabeculotomy, goniotomy,
cryocyclothermy of ciliary body, laser cyclodestruction.
Treatment of secondary angle closure glaucoma depends on the cause.
DIABETES AND THE EYE
Diabetic retinopathy is a late organ complication in diabetes showing up after the
first 10-20 years of the disease. In industrialized countries it is one of the most
frequent causes of blindness (15-20%). About 5% of diabetic patients will
eventually go blind. The long term prognosis for diabetics is poor anyway.
12
Microangiopathy is a fundamental aspect of pathophysiology in diabetes. Involved
capillaries are dilated with the occurrence of microaneurysms, obliteration and
inappropriate perfusion followed by retinal hypoxia.
The clinical picture is as follows:
1. Microaneurysms
2. Diabetic phlebopathy
3. Hemorrhages
4. Soft cotton-wool spots
5. Hard cotton-wool spots
6. Retinal edema, diabetic maculopathy
7. Neovascularization
There are two types of diabetic retinopathy:
1. Simple diabetic retinopathy: benign and local retinal changes
This occurs in 90% of diabetics, progression is slow.The majority of patients
consequently suffer from blurred vision because of diabetic maculopathy.
Progression towards blindness is rare. Diabetic microangiopathy is a typical sign
in these cases .
2. Preprolipherative and prolipherative diabetic retinopathy
In preprolipherative diabetic retinopathy there are phlebopathia, soft cotton-wool
spots, hemorrhages, microaneurysms and retinal edema. In 50% of these
patients, the finding progresses towards the prolipherative stage represented by
fibroprolipherative changes and newly formed blood vessels spreading in the
vitreal space. Vitreal hemorrhages are quite often a cause of visual deterioration
as well as retinal detachment and secondary glaucoma caused by neovascular
changes in the trabecular meshwork. About 50% of these patients go ultimately
blind.
Treatment
Prevention does matter. Maintaining the appropriate blood glucose level and
regular care by an ophthalmologist can make a difference in treating retinopathy.
In the preprolipherative stage panretinal laser photocoagulation is often used. In
13
advanced stages (intravitreal hemorrhage, retinal detachment, fibrovascular
prolipheration) surgery is inevitable (pars plana vitrectomy, removal of preretinal
membranes, laser coagulation and retinal detachment surgery). Co-operation
between ophthalmologist and internist is fundamental.
Intraocular inflammation
Intraocular inflammation can involve the whole uvea (panuveitis) or the anterior
part exclusively - anterior uveitis (iritis, iridocyclitis, cyclitis), intermediate uveitis
(pars planitis, posterior cyclitis, vitritis, peripheral choroiditis), or posterior part
(choroiditis, chorioretinitis).
There are granulomatous and non-granulomatous types of uveitis. According to
etiology there are exogenous (trauma) and endogenous ones.
Types of endogenous uveitis
Uveitis in systemic diseases (tuberculosis, sarcoidosis)
Parasitic infection (Toxocarosis)
Viral infections (e.g. herpes simplex, rubella)
Mycotic infections (e.g. candidosis)
Idiopatic uveitis
According to the clinical picture there are acute and chronic uveitis (the latter lasts
6 wks. or longer).
Anterior uveitis
Acute inflammation of anterior uveal part
Pain in bulbus, photophobia, lacrymation
Ciliary body hyperemia
Alteration of iris color and surface
Precipitates on endothelium, hypopyon, inflammation debris in anterior chamber
or vitreous, posterior synechiae, pupil occlusion
Narrow pupil with delayed reaction to light
Decreased intraocular pressure because of low aqueous humor production
Blurred vision
14
Treatment: mydriatics, corticosteroids,(drops or as parabulbar injection). If
etiology is known the treatment is more specific (eg. virostatics)
Posterior uveitis
Posterior uveitis invariably causes decreased vision (decreased visual acuity,
metamorphosis, scotoma). The introductory phase of the inflammation is slow
and painless. Ophthalmoscopically there are vitreal opacities. In choroidal
involvement, there are fluffy yellow-grayish spots which progress to chorioretinitis.
When healed a scar remains.
Treatment is according to the etiological cause.
Sympathetic ophthalmia
It is chronic granulomatous inflammation of the fellow eye, that may follow a
perforation of the diseased eye after months or years. This injured eye usually
shows a prolonged slight irritation while the fellow eye experiences the formation
of corneal precipitates and iritis. The previously injured eye is the sympathetic
eye, while the fellow eye is the sympathized one. Etiology stays unclear. The only
prevention is early removal of a globe with devastating injury. Treatment
comprises local and systemic use of steroids and mydriatics.
Panuveitis
The inflammatory involvement of the uveal tract is seen in sarcoidosis,
toxoplasmosis, tuberculosis, sympathetic ophthalmia, etc.
Endophthalmitis
Endophthalmitis is a serious inflammatory disorder of the eye. It is mostly the
exogenous type we are likely to come across (postoperative or post-traumatic), it
is rarely endogenous,when an infection is spread by blood. It is not only infectious
agents that may cause endophthalmitis, but also for example, lens material left
intraocularly during cataract surgery (sterile edophthalmitis). The clinical picture
shows blurred vision, vitritis, pain. In infectious endophthalmitis, antibiotics are
used intravitreally, in worsening cases, vitrectomy is inevitable. Antibiotics are
administered into the vitreous cavity and intravenously. In sterile endophthalmitis
corticosterois are used.
15
INTRAOCULAR TUMORS
Malignant melanoma
The incidence of melanoma in uveal tissue occurs in about 5-7 people per one
million inhabitants. In about 80% the choroid is affected, in 10-15 % the ciliary
body. It occurs mostly in people over the age of fifty. The most frequent coexisting risk factors are uveal nevi, neurofibromatosis, congenital melanocytosis,
etc.The clinical picture depends on the tumor location. Uveal melanoma of the
iris and the ciliary body may be present without any clinical signs for a long time.
It can be detected accidentally when a patient is scanned for a different eye
disease or because of the appearance of secondary complications (retinal
detachment, glaucoma, complicated cataracts, etc.). The same applies for
patients with uveal melanoma affecting the choroid.
Iris melanoma
It can circumscribe or diffuse. The diagnosis is based on its growth and increased
vascularization. In differential diagnosis, the iris cyst, iris nevi and juvenile
granulomatosis must be considered. Treatment can be iridectomy or
iridocyclectomy (depending on the tumor size), in large tumors the eye is
removed.
Melanoma of ciliary body
Typical clinical signs are dilated blood vessels in a location of the tumor and lens
induced astigmatism due to the mechanical effect of the tumor. There can also be
decreased intraocular pressure, lens subluxation, unilateral cataract. Under
examination, the nodular pigmented mass expanding towards the lens, anterior
chamber or vitreous is found. Ring melanoma is rare. In differential diagnosis, we
should consider cysts and inflammation.
Choroidal melanoma
It usually appears as a round shaped pigmentary or nonpigmentary mass. When
Bruch’s membrane is invaded, the tumor forms a typical mushroom shape. Vitreal
hemorrhage, pigmentary cells in vitreus, retinal detachment and secondary
16
glaucoma can appear later. Melanoma can spread through sclera extraocularly.
In differential diagnosis, the possibility of choroidal nevi, hemangiona, metastatic
tissue and posterior scleritis should be evaluated.
An examination for melanoma consists of biomicroscopy, gonioscopy,
ophhalmoscopy, fluorescein angiography, sonography, MRI, CT.
Treatment of melanoma depends on its size, location, shape, visual acuity, age of
patient and his/her overall physical status. Radiotherapy (brachytherapy,
teletherapy), fotocoagulation, diathermy and cryotherapy are most frequent
therapeutic procedures. Surgery consists of tumor resection techniques, bulbus
removal or orbital exenteration.
TRAUMATOLOGY
Eye trauma can be mechanical or caused by radiation, heat, electricity or
chemicals.
In mechanical trauma can be seen: disorders of conjunctiva, sclera, perforating
eye injury, recurrent erosions of cornea, non-perforating eye injury of the cornea
or sclera.
In superficial injuries desinfection or antibiotic ointments are used. In deep nonperforating eye injuries, antibiotic eye ointments are used, followed by surgical
suture if required. The eye is patched. In perforating injuries, there is a threat of
endophthalmitis leading to a serious decrease of vision. First aid consists of
binocular patching the immobilized the eyes. Perforation must be dealt with
surgically.
The occurrence of a foreign body in the conjunctiva and cornea is quite frequent.
It may cause remarkable discomfort to the patient: lacrimation, photophobia, pain,
blepharospasm. A foreign body on the conjuctival surface or fixed in the
conjunctiva or cornea, causes red eye syndrome. Treatment requires removal
and instillation of antiseptic or antibiotic drops, ointment and patching.
17
A perforating injury with an intraocular foreign body is a particularly serious one.
Searching for a foreign body present in the eye is facilitated by taking a detailed
history of the trauma, using ophhalmoscopy, and when opacities of optical eye
media develop, performing X-ray, MR or ultrasonography.
Instant surgical treatment is essential. Extraction of the foreign body can be
delayed (7-10 days after trauma). Foreign body is removed by special
instruments similar to a pair of tweezers via pars plana, together with vitrectomy.
If a metal foreign body is freely floating in the vitreous,an adopted magnet probe
can be used.
Eye contusion causes bulbus compression and decompression followed by an
elevation of intraocular pressure, tissue distortion and blood vessel spasms.
Visual loss is reversible or irreversible according to the degree of injury. If the
outside pressure is excessive, rupture of the globe can occur and eye atrophy
may follow.
The eye can be affected by various types of radiation (infrared, UV, ionizing, laser
or sun-emitted).
Acid and lye can cause serious injuries to the eye (coagulating and coliquating
necrosis respectively). Adequate first- aid matters. Instilling a lot of water dilutes
the chemical. Residual material (e.g. mortar) must be removed. That involves the
careful eversion of the upper eye lid. Neglecting residual material may cause an
irreversible injury leading to corneal opacities, conjunctival scarring and shrinking
(symblepharon) Surgery can be helpful in dealing with late consequences of the
above types of trauma. However, the overall outcome of keratoplasty and plastic
surgery of the conjunctiva is rather unpredictable.
18
STRABISMUS AND AMBLYOPIA
Strabismus (heterotropia) is a sensory and muscular disorder affecting both
eyes. Under normal conditions, the eyes stay parallel and balanced, allowing
objects to be projected to macular regions. In pathological circumstances, when
the bulbus is not in a parallel position, the outer objects are projected elsewhere.
The degree of diversion of the bulbus is equal to the number of degrees when
measuring the mutual position of both eyes.
The parallel position of the eyes permits binocular vision. Simple binocular vision
represents an ability to see one object; simultaneous vision allows the perception
of one object when observed by both eyes. Fusion is the ability to merge the
perception of one object as seen by both eyes simultaneously. Stereopsis allows
perceiving three-dimensional objects.
The development of visual functions in a child takes a couple of years and is
finalized at about five years old.
Strabismus is concomitant and incomitant:
Concomitant strabismus
According to the direction of deviation, there is convergent strabismus (ezotropia)
or divergent strabismus (exotropia). In combined forms with vertical deviation,
there are sursumvergens and deorsumvergens types.
Treatment aims to establish the parallel position of the eyes and the introduction
of binocular vision. Refractive errors should be corrected, pleoptic techniques
(amblyopia treatment) and ortoptic techniques (binocular vision facilitation) are
used, supported by surgery .
19
Incomitans (paralytic) strabismus
The movement of the bulbus is limited because of neural palsy, myastenia,
myogenic palsy, etc. There is diplopia depending on the direction of the eyes,
compensating head postures avoiding diplopia are possible.
AMBLYOPIA
This represents an abnormal development of visual function characterized by a
decreased visual acuity despite appropriate optical correction, with no other
clinical finding found in the eye . According to the mechanisms involved, there are
congenital types (up to four years old) and amblyopia that follows restricted
stimulation of the macula because of some additional disorder (it appears later
when the full development of visual function has occured).
Refractive errors and correction
The relation of the globe length to the optical parameters of the eye tissue
concerned, determinates eye refraction. The cornea, anterior chamber, lens and
vitreous form the optic system of the eye. In the emetropic eye, incoming light
beams are projected on the retina. This is allowed by an appropriate relation
between the optical parameters of the eye and its length. If that relation is not
balanced, a refractive error emerges (ametropia). In ametropia, incoming light is
not projected on the retina causing the inability to focus.
There are refractive ametropia (normal eye length but erroneous refraction) and
longitudinal ametropia (inadequate eye length).
Three types of refractive errors
Far-sightedness (hypermetropia) - incoming light beams are merged behind the
retina
Near-sightedness (hypometropia) - incoming light beams are merged before the
retina
Astigmatism – different refraction in various parts of the eye
Hypermetropia is corrected by convex , hypometropia by concave and
astigmatism by cylindrical glasses.
20
Presbyopia
Aging brings the decreasing ability to focus. It can cause cephalea, and fatigue
when struggling to focus while reading. It usually occurs at around 40 years of
age. Appropriate refraction and the use of spectacles brings adequate comfort to
the person.
Refraction is based on subjective and objective methods. Objective methods
consist of ophhalmoscopy and sciascopy. Refractometry tests the overall eye
refraction and a keratometer reveals the magnitude of corneal astigmatism.
Incorrect refraction results may consequently cause a lot of problems to the
patient when prescribing glasses (cephalea, fatigue, etc.). Spectacles and contact
lenses are the main means of correcting refraction disorders. Two types of
surgery can assist in correcting disorders: corneal surgery and intraocular
surgery. Corneal surgery comprises excimer laser, thermocoagulation or
refractive incisions. Intraocular surgery allows the removal of the lens restoring
emetropia by the implantation of the appropriate intraocular lens. In near –
sighted patients ,an intraocular contact lens is put on top of the patient´s lens or a
phakic intraocular lens is implanted into the anterior chamber. Excimer laser
procedures utilize a UV light beam of 193 nm wave length. It allows the removal
of a superficial corneal layer causing the desired change in corneal refraction.
There are two techniques currently in use. PRK (photorefractive keratectomy) and
LASIK (laser in situ keratomileussis). PRK is suitable for refractive errors up to 5
D. When corneal epithelium is removed, a laser beam forms a new corneal
surface. LASIK is mostly used for correcting errors more than 3 D. After a thin
layer of superficial cornea in a round shape is temporary lifted off and the corneal
stroma is exposed, a laser beam is used.
SOCIAL OPHTHALMOLOGY
Severe visual impairment and blindness
Severe visual impairment and blindness are a serious worldwide concern.
According to the WHO, there are about 40 million blind people worldwide. The
prevalence of visual impairment is 10-40 times higher in the developing world
21
/ranging between 0.4-8.8% / than in industrialized countries . Cataract is a
leading cause, followed by infectious diseases and malnutrition. The prevalence
of blindness in industrialized world is 0.2%, mostly caused by macular
degeneration, diabetic retinopathy and glaucoma.
Categories of visual impairment differ in various countries. Absolute blindness is
easy to determine. However, people partially sighted face various difficulties
interfering with their social life, working opportunities, adaptation to their living
conditions, etc. Modifying factors comprise age, when visual impairment
emerged, education, physical status, other diseases, influence of the family and
the environment.
For practical reasons, there are two grades of blindness distinguished:
Absolute blindness – ranges from total amaurosis to false perception of the
direction of incoming light.
Practical blindness – means visual acuity worse then 3/60 or restriction of a visual
field to 10 degrees or less.
The visual rehabilitation of handicapped people very much depends on their age.
The goal is to cultivate and encourage their use of residual vision, and to fuller
develop their hearing and touch. The co-operation of ophthalmologists with
specialized institutions is essential. These are nursery schools, elementary
schools and secondary schools for the visually handicapped, apprentice schools
for the visually handicapped (to become an upholsterer, book binder, technician)
and rehabilitation centers for those who became visually handicapped during their
productive life.
The use and availability of rehabilitating and compensating tools for the visually
handicapped plays a major role. The former help the partially sighted (spectacles,
loupes, adjusted and modified computers), the latter are aimed at blind people
(white walking sticks, clocks for the blind, tape players, recorded books, books in
Braill and the use of seeing-eye dogs).
The rehabilitation of visually handicapped people is individually determined to
accomplish all the requirements of schooling, involvement in the life of society
22
and in work, and to allow for consequent guaranties for obtaining appropriate
health care and social benefits after retirement.
23
REFERENCES
Kanski, J.J.: Clinical Ophthalmology: a systemic approach. Fourth edition.
Butterworth-Heinamann Ltd. 1999, p. 673.
Kanski, J.J., Nischal, K.K.: Clinical Ophthalmology: A test yourself atlas.
Butterworth-Heinamann Ltd. 1995, p. 186